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1 definition by DFR

A “Deadfire” is a military word meaning the following:

Deadfiring is firing multiple missiles or other projectiles without having a lock on or aiming. If firing in Deadfire mode, you are usually aiming in the general area of the target and firing. Used in high stress situations, as well as a scare tactic.

So in other words you aim to basically to it and everything around it, with massive firepower.
OMG, I owned that Noob with a deadfire of missles
by DFR April 29, 2006